A semiconductor device such as an ID chip that can transmit and receive data such as identifying information wirelessly has been coming into practical use in various areas, and the market of such a semiconductor device as a communication information terminal of a new mode is anticipated to grow further. An ID chip is also called a wireless tag, an RFID (Radio frequency identification) tag or an IC tag, and a type having an antenna and an integrated circuit formed by using a semiconductor substrate is coming into practical use at present.
There are two cases in forming an ID chip, where an integrated circuit and an antenna formed separately are connected later, and where an integrated circuit and an antenna are formed so as to range over one substrate.
As for the ID chip formed by connecting an integrated circuit and an antenna which are first formed separately, defects are easily caused at the connection portion of the integrated circuit and the antenna, and thus it is difficult to increase the process yield. Further, an ID chip is expected to be attached to a flexible material such as paper or plastic depending on its use. Accordingly, a stress is applied, in some cases, to a substrate where an integrated circuit is formed in using an ID chip, even though the integrated circuit is favorably connected to the antenna. Thus, there is a problem that defects are caused easily by the stress, which leads to low reliability.
On the other hand, in an ID chip in which an integrated circuit and an antenna are formed on a substrate, such a defect in a connection portion is not easily caused, different from one in which an integrated circuit and an antenna are formed separately. However, if the number of ID chips obtained from one substrate is to be secured, the area for forming an antenna is limited accordingly. Therefore, it is difficult to form a highly advantageous antenna due to the size limit of an antenna.
A semiconductor substrate used for forming an integrated circuit is generally poor in flexibility and mechanical strength, which is a drawback. However, the mechanical strength can be improved to some extent by reducing the area of the integrated circuit itself. However, the case is not favorable, since securing a circuit scale is difficult and the use of an ID chip is limited. Therefore, it is not favorable that the area of an integrated circuit is reduced when securing the circuit scale of the integrated circuit without careful thought.
The present invention has been made in view of the above described problems. It is an object of the present invention to provide an ID chip in which gain of an antenna is increased and the mechanical strength of an integrated circuit can be enhanced without suppressing a circuit scale. Further, the present invention relates to a packing material, a tag, a certificate, a bank note, securities and the like using the ID chip.